Changing VG primary path

[kurt_karl]

Hi,

We're are planing to do a disk load balancing on all our VG's that our Informix 9 databases are using.  These vg's are using EVA 4400 virtual disks.   Right now 80 percent of our production databases vg's/chunks are using the same primary path group "/dev/dsk/c4t???? and we want to alternate each vg's primary path to use other Alternate link for load balancing.

Our plan is,  run a vgreduce on the volume group current primary path so it will use the next alternate path then run vgextend from the original primary path so to put back that path again for re-use in case of fail-over.

Would this be the right approach?  The last time we did these on our test database it works fine and the test database recognized the new vg primary path but when we run these again on a production database,  the database wont go online and treats the newly adjusted vg as bad chunks.  We are afraid to continue these steps to other production database vg's now.

Any suggestions would be greatly appreciated

Kurt

P.S. This thread has been moved from Storage Area Networks (SAN) (Enterprise) to HP-UX > LVM and VxVM. - Hp Forum Moderator

[Arnaud Delaloy]

hello,

(I'm  assuming you are using HP-UX 11i v& or v2, with legacy disk device names)

 if you just want to  switch the primary paths from your PVs, there is no need to vgextend/vreduce the PVs :  the pvchange -s /dev/dsk/c command  brings an alternate to primary path.

(it doesn't modify the VG headers, unlike a vgextend/vgreduce)

but if you have EVA Securepath installed, it's kind of a moot point ; all the paths are used anyway, and the LVM commands are just for legacy reasons.

 you can see the primary/alternate paths the from the "physical volumes" section on vgdisplay -v  (sorry, my term locale is in French..)

   --- Volumes physiques ---

   Nom PV                      /dev/dsk/c23t3d7   

Nom PV                      /dev/dsk/c25t3d7 Lien secondaire   

Nom PV                      /dev/dsk/c39t3d7 Lien secondaire   

Nom PV                      /dev/dsk/c31t3d7 Lien secondaire   

Nom PV                      /dev/dsk/c33t3d7 Lien secondaire   

Nom PV                      /dev/dsk/c15t3d7 Lien secondaire   

Nom PV                      /dev/dsk/c17t3d7 Lien secondaire   

Nom PV                      /dev/dsk/c41t3d7 Lien secondaire   

Etat PV                     disponible   

PE total                    3198   

PE disponible               3198   

Autocommutateur             En fonction   

Proactive Polling           On

[Torsten.]

Still using 11.11 or 11.23?

With or without autopath?

The vgreduce/vgextend method will give you the expected result, the pvchange will give it too, but only until the next boot.

[kurt_karl]

HI,

Were running hpux 11.23 with Autopatch/Autoswitch "On".  Maybe this is why when we apply both these (vgreduce and vgextend) commands on our production database it says that the vg/chunk is offline because the other admin run a pvchange instead of vgreduce and didn't do any server reboot then I did run the vgreduced and vgextend to the same primary path for I didn't know that the other admin already run a pvchange.  Do you think this is why the database treats this as a bad chunk?  we end up doing a warm restore on the database.

[Torsten.]

First you should check if you have autopath/secure path installed, try to run

# autopath display -r

[kurt_karl]

Hi Torten,

we dont have autopath installed on the machine. is this something I should be installing? if yes, it this something for purchase? thank you.

[Torsten.]

AutoPath is the multipathing software for active/active arrays for use with 11.23.

But why not upgrading to 11.31?

[kurt_karl]

Hi,

We are on summer time. Does 11.31 has the AutoPath included already?

Thanks
Kurt

[Torsten.]

Version 11.31 has native multipathing, so the server will do load balancing accross the paths.

[kurt_karl]

We are planing to do a disk load balancing using vgreduce and vgexport on some of our disk. I know if I use the vgreduce on our current primary path it will use the first Alternate link on the list as the new primary path. Is there a way/command to tell the system to use a specific Alternate link to be our new primary path using vgreduce or it is always the first Alternate link on the list that the system will use? thank you

[Torsten. · Accepted solution]

You sort it by vgreduce/vgextend, pvchange will chenge it temporary only.

But as a long term solution you should go to hp-ux 11.31 with a real load balacing ...

For the moment make sure you keep both controllers busy, not only a single controller.

The tool "evainfo" can help you to find out what path belongs to what controller, you will find the tool as part of P6000 Command View at software.hp.com.

Example from the webpage:

# ./evainfo -a -p

Devicefile                       Array                       WWNN              Capacity        Controller/Port/Mode

/dev/rdisk/disk5165      5000-1FE1-5002-E1B0 6005-08B4-0010-2AB1-0000-F000-0053-0000 
10240MB       Ctl-B/FP-2/NonOptimized
/dev/rdsk/c232t15d7     5000-1FE1-5002-E1B0 6005-08B4-0010-2AB1-0000-F000-0053-0000
10240MB       Ctl-A/FP-1/Optimized
/dev/rdsk/c233t15d7     5000-1FE1-5002-E1B0 6005-08B4-0010-2AB1-0000-F000-0053-0000
10240MB       Ctl-B/FP-2/NonOptimized
/dev/rdsk/c230t15d7     5000-1FE1-5002-E1B0 6005-08B4-0010-2AB1-0000-F000-0053-0000
10240MB       Ctl-A/FP-1/Optimized
/dev/rdsk/c231t15d7     5000-1FE1-5002-E1B0 6005-08B4-0010-2AB1-0000-F000-0053-0000
10240MB       Ctl-B/FP-2/NonOptimized

Since the EVA is an ALUA device, you can see 2 pathes to controller A as OPTIMIZED, 2 to controller B as NonOptimized (standby).

[kurt_karl]

That's my concern Torsten. I'm afraid if I run the vgreduce on some of our vg's it will end up using the same controller. Since most of our vg's when we look up the Alternate links they all end up having the same path on the first Alternate link. So once we are done with the load balancing they might end up again using the same primary path because of the Alternate links. But how would you know which path uses which controllers? is there a command line for this? thank you

[Torsten.]

I added the info to my previous post.

[kurt_karl]

Thank for the quick response Torsten. I dont have that software installed. I will try to install one today if I can but one quick question if you wont mind. If you say "You sort it by vgreduce/vgextend" what do you mean by this? does it mean that I have to do several vgreduce comands on the same vg until I get the right Alternate link from the list that I want to be our new Primary link then add those missing links back using vgextends?

[Torsten.]

>> does it mean that I have to do several vgreduce comands on the same vg until I get the right Alternate link from the list that I want to be our new Primary link then add those missing links back using vgextends?

Exactly.